I knew before I started reading the posts that the advise was going to be all over the place. If anything we will confuse the issue. My two cents are no different.

First of all when it comes to towing and mileage there is no substitute for diesel. Now for my story. I had a 2500 Dodge Ram Cummins that towed wonderfully. It replaced an F250 V-10 that would not hold speed in hill situations and got about 6 mpg towing. I was in a similar situation with pending steering component repairs and decided to get a new vehicle. Since I drive a company car the vehicle would be the wife's daily driver. She did not want a clunky truck to drive around so I gave her a choice. She could get anything we could afford AND it had to be diesel. After considering the few choices out there we went with the VW Touareg. It's mid sized and my 6'3" son fits just fine in the back seat. Not so in our 4runner. It has all wheel drive so absolutely no wheel spin issues at the ramp. It has a 7700lb tow rating. With a 3 liter diesel the thing gets about 31 mpg at 65 mph. We get about 24 in town. The torque is awesome for towing with a fairly large and flat torque curve that is mated to an eight speed transmision so it's never searching for a gear. It pulls strong and keeps speed going up grades. This is the type of tow vehicle that passes slow people in motorhomes on a two lane road. The vehicle has a substantial all around feel to it. From the solid feel of the door closing to the solid tow stability. It's a rocket ship that feels equally well doing 85+ mph. We absolutely love the vehicle and it's cool not driving a vehicle that everyone else has. It's hard to rub two of them together. The wife is excited because the 2013 Porche Cheyene which is made in the same factory along with the Audi Q7 will have the diesel next year. I can dream.

Good luck in putting a consensus from all the info thats conflicting. In the end you'll have to use your gut.